1. Field of the Invention
The present invention relates to an impeller for a radial-flow heat dissipating fan. In particular, the present invention relates to an impeller for a radial-flow heat dissipating fan with increased air inlet amount.
2. Description of Related Art
FIG. 1 of the drawings illustrates a conventional radial-flow heat dissipating fan. The radial-flow heat dissipating fan in FIG. 1 comprises a casing 1 and a cover 2. The casing 1 includes a compartment 11 and a side outlet 12. The cover 2 is mounted to the casing 1 and includes an inlet 21. An impeller 3 is rotatably mounted in the compartment 11 of the casing 1 and includes a hub 31, a supporting member 32 extending from the hub 31, and a plurality of blades 33 each having an edge mounted on a side of the supporting member 32.
FIG. 2 illustrates another conventional radial-flow heat dissipating fan, wherein a connecting ring 34 extends across the other edges of the blades 33 to improve the strength. In operation, turning of the blades 33 of the impeller 3 drives axial airflow into the casing 1 via the inlet 21 of the cover 2. Then, the axial airflow is driven by the blades 33 to exit the casing 1 via the side outlet 12 for dissipating an object such as a fin.
Although the above radial-flow heat dissipating fans are widely used in computers, there are still several problems. First, the other edge 33a of each blade 33 is located at the same level as a top face of the hub 31. After assembly, the top face of the hub 31 is very close to the inlet 21 of the cover 2. Thus, the incoming air can only pass through the inlet 21 via the gap between the blades 33, resulting in limitation to the amount of the incoming axial airflow. In this case, if the other edge 33a of each blade 33 has a relatively long radial length, the other edge 33a interferes with entrance of the incoming axial airflow via the inlet 21. The air inlet amount could not be increased, the air outlet amount and the wind pressure are reduced. Secondly, if the other edge 33a of each blade 33 has a relatively long radial length, the incoming axial airflow entering the casing 1 via the inlet 21 is directly guided by the rotation of the edge 33a and thus turns into centrifugal airflow, leading to blowing noise and adversely affect to the rotational efficiency of the impeller.